This invention relates to the processor of a microprogram system, and more particularly to microprocessor capable of executing a high speed processing.
For instructions used in a computer such as a microprocessor, in spite of performing the same operation, for example, an operation for performing the logical product, there are instances where an operand indicates a register and the operand indicates a memory device. Such instructions having different operands are recognized to be quite different from each other in computer of the microprogram system. Accordingly, different microprograms are used in respective cases, or a conditional jump microcode or a conditional next instruction start microcode, where a conditioning portion exists in the microcode so as to change the start of a next instruction, is prepared, depending upon the kind of operands, thus discriminating from each other instructions having different operands in the microprogram.
In a conventional microprogram processor having such a function, when the operand indicates a memory, a request for access to the memory can be first made at a next step at least one clock later after a next instruction start signal has been outputted from a next instruction start condition judgement decoder. For this reason, the start of access to the memory is delayed whereby the completion of execution of the instruction is also delayed, with the result that the instruction execution time will be prolonged.
As just described above, the conventional microprogram processor has the problem that access to the memory is delayed and thus the instruction execution time is prolonged, failing to satisfy high speed requirements.